So far I've made 16 sales on TCGplayer, 11 more on Mercari and Ebay I've been on for years and periodically put stuff up on there to sell also.
Across the three different platforms I've got 100% ratings on them all!
Everything has been going smoothly and I've been finding that I'm able to drum up more sales when I listing in multiple places.
I've even sold a few things on Facebook marketplace too but I haven't really been trying too hard to list there just because it takes so much time and work to list across the other three platforms.